Die for die casting and method of making the same



June 16, 1931.

V. L. SODERBERG DIE FOR DIE CASTING AND METHOD OF MAKING THE SAME Filed May 26, 1927 Patented June 16, 1931 UNITED STATES VICTOR L. SODERBERG, OF DETROIT, MICHIGAN DIE FOR DIE CASTING AND METHOD OF MAKING THE SAME Application filed May 26, 1927. Serial No. 194,519.

Heretofore dies for use in the production of die castings have been cut out of steel in order to secure durability. This has made the cost of such dies very higlrcompared to )1 5 what it would be if they were made of copper or brass or some other metal that can be cut more easily. Furthermore, in the tempering of steel dies they are apt to warp or crack, or both. The metals that can be fashioned more easily than can steel are not suitable for use in the manufacture of these dies, since they either oxidize quickly when castings are made in the dies or show an affinity for the metal that is being cast.

One of the objects of the present invention is to make it possible to use metals that can be cut more easily than the steel heretofore employed in the production of dies for die cast ings, so as greatly to reduce the cost of such dies. I

I have found that what may be termed the inferior materials can be made available for the manufacture of dies, thus greatly reducing the cost of cutting the dies, by electrodepositing a hard metal, preferably chromium, on the surfaces exposed in the die cavities. Surfaces so coated show no athnity for the metals ordinarily cast, nor do they oxidize or form other compounds that will result in a flaking off or other deterioration.

Therefore, viewed in one of its aspects, the present invention may be said to have for its object to produce a die consisting of a body member of comparatively soft cast or'forged material in which the casting is done, and a facing of hard resistant material in the die cavity.

Chromium in the wearing face of a die casting die is more durable than high grade 40 steel, and casting releases and clears itself better from a chromium surface than from a steel surface. Therefore even steel dies may advantageously be plated with chromium,

thus obviating the necessity of hardening or tempering them and avoiding the danger of warping or cracking while, at the same time,

dies better than ordinary perfect steel dies, are produced.

Therefore, viewed in one of its aspects, the

9 present invention may be said to have for its object to treat steel dies for die casting in such a manner as to overcome the need for tempering or hardening the steel and, at the same time. increase the eiiiciency of the dies and make them more durable.

Since the body of the die constitutes simply a backing for the layer of chromium and may therefore be of any material having the requisite strength and toughness, the die may be cast or forged. The present invention in some of its aspects, may be said to have for its object to permit cast or forged dies to be successfully used for die casting.

In many instances the die cavities will be of extremely irregular configuration. Another object of the present invention is to provide means for insuring a uniform deposit of chromium around all parts of the die cavity, as well in deep narrow depressions as on broad and easily accessible faces.

The various features of novelty whereby my invention is characterized will hereinafter he pointed out with particularity in the claims; but, for a full understanding of my invention and of its objects and advantages, reference may be had to the following detailed description taken in connection with the accompanying drawings, wherein:

Figure 1 is a plan view of a die block having associated therewith a. special anode preparatory to the plating process; Fig. 2 is a section taken on line 22 of Fig. 1;

Fig. 3 is a section taken on line 3 30f 1, on a larger scale, showing the completed product; and Fig. 4 is a seetion,jon a smaller scale, through the die and a. second form of anode, on the sameplane as Fig- 3.

Referring to the drawings, 1 represents a block in which one-half of the die cavity 2 is cut. This block may be made of copper, brass, cast iron, wrought iron, soft steel or any material that lends itself readily to being cut, cast or forged to produce die cavities; or it may bemade of the high grade steel usually employed for this purpose. The block has the usual holes 3 for receiving the dowel pins on the companion block. After the die cavity has been cut I place in the same an anode so that, when the block is placed in a bath suitable for depositing 8 in the die block.

chromium and is connected in the circuit as the cathode, a coating of chromium will be deposited as a lining for the die cavity. I mount the anode on pegs I of wood or the like, inserting these pegs in the openings If the pegs are a tight fit the anode may be accurately positioned with respect to the die cavity with the assurance that it will so remain until the plating operation is complete.

To secure the proper distribution and density of current the anode must be specially shaped. Thus in the illustration, the die is shown as one employed for the casting of ornamental dogs that are mounted on radiator caps, and the anode shown as being built up out of wires as will later be explained, an anode similar in shape but slightly smaller than the die cavity, may be employed. The anode illustrated consists of a main wire 5 extending throughout the length of the cavity, from the nose to the tail; a second wire 6 extending from within the cavity for the hind legs forwardly through the bottom and into the cavity for one of the front legs, and a small. wire 7 extending from one .of the other wires into the cavity for the second fore leg. The wires in the comparatively deep narrow cavities. as best shown in Fig. 2, are placed near the bottom of these cavities. The cavity in which the wire 6 is located is deeper than that containing the wire 7 and therefore the latter wire is made smaller in diameter than the other. Furthermore, the cavity for the face portion of the dog is shallow, comparing depth to width, and the end of the wire 5 is flattened as indicated at 8 so as to increase its width.

The wire 7 and the front ends of the wires 5 and 6 give sufiicient distribution for the front portion of the die cavity. In the rear thiqh portion ofthe cavity I provide an additional anode element in the form of a U-shaped part 9 on the end of one of the supporting wires, 10 for the anode. The supporting wire 10 is fastened at one end to one of the pegs and at the other end to the wire 5 or 6 or both. Extending from the other peg is a supporting wire 11 fastened to the wire 6.

It is evident that considerable skill is required to design an anode of the type just described and therefore I shall explain another type and the method of making it. A layer of wax may be applied to the die faces, reducing the size of the die cavity by any desired amount. The die is then used as a mold in which a pattern is cast in plaster or other suitable material. An anode is then cast from the pattern. the anode being smaller than but of the same shape as the die cavity as shown at A in Fig. 4. Conse quently when the anode is properly posi tioned in the cavity, every point in the surface to be plated will be at the same distance from the anode as is every other point, and a perfect coating will be deposited in the subsequent plating operation.

As heretofore explained, the prepared die block, with the anode in place, is placed in a proper bath and connected in an electrolyte circuit of such a character that the die cavity will receive a lining of metallic chromium of any desired thickness. After the chromium has been deposited, the cavity has a lining of chromium such as indicated at 12 in Fig. 3, although in the drawing the thickness of the lining is greatly exaggerated.

'lhecoinpleted die, produced at an expense much less than one cut out of steel, if of some other metal than the steel heretofore usually employed, possesses all of the advantages of the latter, notbeing affected by molten metal cast in the same or by the heat imposed upon the same by such metal; and in addition, the plated die is more durable than a die having a steel face, allows the casting to release and clear itself more readily therefrom, and will not be warped or cracked as hardened steel dies sometimes are. If the die originally was of high grade steel, it has been made more efficient and more durable and has not been placed in jeopardy by reason of a tempering or hardening operation.v

I do not desire to be limited to the details illustrated and described, although I have described with particularity a preferred manner of carrying outmy invention; but intend to cover all forms and methods coming within the definitions of my invention constituting the appended claims. Furthermore, while chromium is the metal I prefer to use for plating the dies, I do not Wish to be limited to this metal since other hard metals will answer.

Iclaim:

1. The method of making a die for die casting which consists in fashioning a die cavity in a block of metal easily cut but unsuitable for exposure as a face for a die cavity, supporting on and insulating from the block a conductor having elements of various sizes shapes and locations depending on the nature of the portions of the cavities in which they are located, placing the block and anode in an electrolyte suitable for depositing chromium, and connecting the block as a cathode in a plating circuit in which said conductor is the anode.

2. The combination with a metal block containing a die cavity and holes for dowel pins,

tion.

VICTOR L. SODERBERG. 

